1. Field of the Invention
The present invention relates to a distal endoscope part, or more particularly, a distal endoscope part characterized by a portion thereof in which light emitting diodes serving as an illuminating means are placed.
2. Description of the Related Art
Structures having a light emitting source such as light emitting diodes incorporated as an illuminating means in a distal endoscope part have been proposed in the past.
For example, Japanese Unexamined Patent Publication No. 63-260526 describes a distal endoscope part for side viewing in which a plurality of light emitting diodes is placed circumferentially with an objective optical system as a center in order to improve the light emitting characteristic of the distal part.
However, according to the prior art (Japanese Unexamined Patent Publication No. 63-260526), the light emitting diodes are placed on a spherical surface on the outer circumference of an endoscope. The plurality of light emitting diodes must be attached one by one to a distal member.
When the light emitting diodes must be attached one by one to the distal endoscope member, there is difficulty in narrowing the spacing between adjoining light emitting diodes. Therefore, a side viewing endoscope having a plurality of light emitting diodes placed on the outer circumference of an objective optical system has a drawback in that the distal part thereof is large in size.
Japanese Unexamined Patent Publication No. 8-117184 proposes a structure having a light emitting source as an illuminating means incorporated in a distal endoscope part. Japanese Utility Model Registration No. 3007137 proposes a structure having light emitting diodes as an illuminating means placed around a camera in a distal part of a tubular examination camera system. In these structures, the light emitting unit is protected with a cover glass or acrylic plate placed on the front surface thereof.
Especially in Japanese Utility Model Registration No. 3007137, the cover glass over the front surfaces of the light emitting diodes also works to render the light emitting diodes watertight.
However, when a watertight structure is realized using a transparent member such as the cover glass described in the prior art, the cover glass must have a thickness large enough to position the perimeter thereof relative to a metallic member to support itself therein. In the structure having the cover glass, therefore, mechanical members must be made larger to a dimension corresponding to the perimeter used for positioning the cover glass.
As described in Japanese Utility Model Registration No. 3007137, a structure has the light emitting diodes, which serve as an illuminating means, placed on the outer circumference of an imaging unit and a transparent member placed on the front surfaces of the light emitting diodes. This poses a problem in that the outer diameter of the distal part must be made larger to a dimension corresponding to the perimeter of the transparent member.
An object of the present invention is to provide a distal endoscope part which makes it possible to realize a side viewing endoscope having a plurality of light emitting diodes placed on the outer circumference of an objective optical system without an increase in the outer diameter of the distal part.
Another object of the present invention is to provide a distal endoscope part which makes it possible to realize a watertight structure without the necessities of placing a transparent member over the front surfaces of the light emitting diodes and of increasing the outer diameter of the distal part.
A distal endoscope part in accordance with the present invention has a plurality of light emitting diodes for supplying illumination light placed as an illuminating means on the outer circumference of an objective optical system. The plurality of light emitting diodes is mounted on a substrate and united therewith. A sub-assembly of the plurality of united light emitting diodes is placed on a plane containing the longitudinal axis of an insertion unit of the endoscope. Consequently, although the side viewing endoscope has the plurality of light emitting diodes placed on the outer circumference of the objective optical system, the outer diameter of the distal part thereof is not large in size.
Other features of the present invention and advantages thereof will be fully apparent from the description below.